Cassette format

VCR Cassettes are files that contain all of the information about the requests and corresponding responses in a human-readable/editable format. A cassette contains an array of HTTP interactions, each of which has the following:

request
- method
- uri
- body
  - encoding
  - string
- headers
response
- status
  - code
  - message
- headers
- body
  - encoding
  - string
- http version
By default, VCR uses YAML to serialize this data. You can configure VCR to use a different serializer, either on a cassette-by-cassette basis, or as a default for all cassettes if you use the default_cassette_options.
VCR supports the following serializers out of the box:
:yaml--Uses ruby's standard library YAML. This may use psych or syck, depending on your ruby installation.
:syck--Uses syck (the ruby 1.8 YAML engine). This is useful when using
VCR on a project that must run in environments where psych is not available
(such as on ruby 1.8), to ensure that syck is always used.
:psych--Uses psych (the new ruby 1.9 YAML engine). This is useful when
you want to ensure that psych is always used.
:json--Uses multi_json
to serialize the cassette data as JSON.
:compressed--Wraps the default YAML serializer with Zlib, writing compressed cassettes to disk.
You can also register a custom serializer using:
VCR.configure do |config| config.cassette_serializers[:my_custom_serializer] = my_serializer end
Your serializer must implement the following methods:
file_extension
serialize(hash)
deserialize(string)

Request/Response data is saved to disk as YAML by default

Given a file named "cassette_yaml.rb" with:

include_http_adapter_for("<http_lib>")

if ARGV.any?
  $server = start_sinatra_app do
    get('/:path') { ARGV[0] + ' ' + params[:path] }
  end
end

require 'vcr'

VCR.configure do |c|
  <configuration>
  c.cassette_library_dir = 'cassettes'
  c.before_record do |i|
    i.request.uri.sub!(/:\d+/, ':7777')
  end
end

VCR.use_cassette('example') do
  make_http_request(:get, "http://localhost:#{$server.port}/foo", nil, 'Accept-Encoding' => 'identity')
  make_http_request(:get, "http://localhost:#{$server.port}/bar", nil, 'Accept-Encoding' => 'identity')
end

When I successfully run ruby cassette_yaml.rb 'Hello'

Then the file "cassettes/example.yml" should contain YAML like:

---
http_interactions:
- request:
    method: get
    uri: http://localhost:7777/foo
    body:
      encoding: UTF-8
      string: ""
    headers:
      Accept-Encoding:
      - identity
  response:
    status:
      code: 200
      message: OK
    headers:
      Content-Type:
      - text/html;charset=utf-8
      Content-Length:
      - "9"
    body:
      encoding: UTF-8
      string: Hello foo
    http_version: "1.1"
  recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
- request:
    method: get
    uri: http://localhost:7777/bar
    body:
      encoding: UTF-8
      string: ""
    headers:
      Accept-Encoding:
      - identity
  response:
    status:
      code: 200
      message: OK
    headers:
      Content-Type:
      - text/html;charset=utf-8
      Content-Length:
      - "9"
    body:
      encoding: UTF-8
      string: Hello bar
    http_version: "1.1"
  recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
recorded_with: VCR 2.0.0

Examples

Request/Response data can be saved as JSON

Given a file named "cassette_json.rb" with:

include_http_adapter_for("net/http")

$server = start_sinatra_app do
  get('/:path') { ARGV[0] + ' ' + params[:path] }
end

require 'vcr'

VCR.configure do |c|
  c.hook_into :webmock
  c.cassette_library_dir = 'cassettes'
  c.before_record do |i|
    i.request.uri.sub!(/:\d+/, ':7777')
  end
  c.default_cassette_options = {
    :match_requests_on => [:method, :host, :path]
  }
end

VCR.use_cassette('example', :serialize_with => :json) do
  puts response_body_for(:get, "http://localhost:#{$server.port}/foo", nil, 'Accept-Encoding' => 'identity')
  puts response_body_for(:get, "http://localhost:#{$server.port}/bar", nil, 'Accept-Encoding' => 'identity')
end

When I run ruby cassette_json.rb 'Hello'

Then the file "cassettes/example.json" should contain JSON like:

{
  "http_interactions": [
    {
      "response": {
        "body": {
          "encoding": "UTF-8",
          "string": "Hello foo"
        },
        "http_version": null,
        "status": { "code": 200, "message": "OK" },
        "headers": {
          "Date": [ "Thu, 27 Oct 2011 06:16:31 GMT" ],
          "Content-Type": [ "text/html;charset=utf-8" ],
          "Content-Length": [ "9" ],
          "Server": [ "WEBrick/1.3.1 (Ruby/1.8.7/2011-06-30)" ],
          "Connection": [ "Keep-Alive" ]
        }
      },
      "request": {
        "uri": "http://localhost:7777/foo",
        "body": {
          "encoding": "UTF-8",
          "string": ""
        },
        "method": "get",
        "headers": {
          "Accept-Encoding": [ "identity" ]
        }
      },
      "recorded_at": "Tue, 01 Nov 2011 04:58:44 GMT"
    },
    {
      "response": {
        "body": {
          "encoding": "UTF-8",
          "string": "Hello bar"
        },
        "http_version": null,
        "status": { "code": 200, "message": "OK" },
        "headers": {
          "Date": [ "Thu, 27 Oct 2011 06:16:31 GMT" ],
          "Content-Type": [ "text/html;charset=utf-8" ],
          "Content-Length": [ "9" ],
          "Server": [ "WEBrick/1.3.1 (Ruby/1.8.7/2011-06-30)" ],
          "Connection": [ "Keep-Alive" ]
        }
      },
      "request": {
        "uri": "http://localhost:7777/bar",
        "body": {
          "encoding": "UTF-8",
          "string": ""
        },
        "method": "get",
        "headers": {
          "Accept-Encoding": [ "identity" ]
        }
      },
      "recorded_at": "Tue, 01 Nov 2011 04:58:44 GMT"
    }
  ],
  "recorded_with": "VCR 2.0.0"
}

When I run ruby cassette_json.rb

Then it should pass with:

Hello foo
Hello bar

Request/Response data can be saved as compressed YAML

Given a file named "cassette_compressed.rb" with:

include_http_adapter_for("net/http")

$server = start_sinatra_app do
  get('/:path') { ARGV[0] + ' ' + params[:path] }
end

require 'vcr'

VCR.configure do |c|
  c.hook_into :webmock
  c.cassette_library_dir = 'cassettes'
  c.before_record do |i|
    i.request.uri.sub!(/:\d+/, ':7777')
  end
  c.default_cassette_options = {
    :match_requests_on => [:method, :host, :path]
  }
end

VCR.use_cassette('example', :serialize_with => :compressed) do
  puts response_body_for(:get, "http://localhost:#{$server.port}/foo", nil, 'Accept-Encoding' => 'identity')
  puts response_body_for(:get, "http://localhost:#{$server.port}/bar", nil, 'Accept-Encoding' => 'identity')
end

When I run ruby cassette_compressed.rb 'Hello'

Then the file "cassettes/example.zz" should contain compressed YAML like:

---
http_interactions:
- request:
    method: get
    uri: http://localhost:7777/foo
    body:
      encoding: UTF-8
      string: ""
    headers:
      Accept-Encoding:
      - identity
  response:
    status:
      code: 200
      message: OK
    headers:
      Content-Type:
      - text/html;charset=utf-8
      Content-Length:
      - "9"
    body:
      encoding: UTF-8
      string: Hello foo
  recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
- request:
    method: get
    uri: http://localhost:7777/bar
    body:
      encoding: UTF-8
      string: ""
    headers:
      Accept-Encoding:
      - identity
  response:
    status:
      code: 200
      message: OK
    headers:
      Content-Type:
      - text/html;charset=utf-8
      Content-Length:
      - "9"
    body:
      encoding: UTF-8
      string: Hello bar
  recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
recorded_with: VCR 2.0.0

When I run ruby cassette_compressed.rb

Then it should pass with:

Hello foo
Hello bar

Request/Response data can be saved using a custom serializer

Given a file named "cassette_ruby.rb" with:

include_http_adapter_for("net/http")

$server = start_sinatra_app do
  get('/:path') { ARGV[0] + ' ' + params[:path] }
end

require 'vcr'

# purely for demonstration purposes; obviously, don't actually
# use ruby #inspect / #eval for your serialization...
ruby_serializer = Object.new
class << ruby_serializer
  def file_extension; "ruby"; end
  def serialize(hash); hash.inspect; end
  def deserialize(string); eval(string); end
end

VCR.configure do |c|
  c.hook_into :webmock
  c.cassette_library_dir = 'cassettes'
  c.cassette_serializers[:ruby] = ruby_serializer
  c.before_record do |i|
    i.request.uri.sub!(/:\d+/, ':7777')
  end
  c.default_cassette_options = {
    :match_requests_on => [:method, :host, :path]
  }
end

VCR.use_cassette('example', :serialize_with => :ruby) do
  puts response_body_for(:get, "http://localhost:#{$server.port}/foo", nil, 'Accept-Encoding' => 'identity')
  puts response_body_for(:get, "http://localhost:#{$server.port}/bar", nil, 'Accept-Encoding' => 'identity')
end

When I run ruby cassette_ruby.rb 'Hello'

Then the file "cassettes/example.ruby" should contain ruby like:

{"http_interactions"=>
  [{"request"=>
     {"method"=>"get",
      "uri"=>"http://localhost:7777/foo",
      "body"=>{"encoding"=>"UTF-8", "string"=>""},
      "headers"=>{"Accept"=>["*/*"], "Accept-Encoding"=>["identity"], "User-Agent"=>["Ruby"]}},
    "response"=>
     {"status"=>{"code"=>200, "message"=>"OK "},
      "headers"=>
       {"Content-Type"=>["text/html;charset=utf-8"],
        "Content-Length"=>["9"],
        "Connection"=>["Keep-Alive"]},
      "body"=>{"encoding"=>"UTF-8", "string"=>"Hello foo"},
      "http_version"=>nil},
    "recorded_at"=>"Tue, 01 Nov 2011 04:58:44 GMT"},
   {"request"=>
     {"method"=>"get",
      "uri"=>"http://localhost:7777/bar",
      "body"=>{"encoding"=>"UTF-8", "string"=>""},
      "headers"=>{"Accept"=>["*/*"], "Accept-Encoding"=>["identity"], "User-Agent"=>["Ruby"]}},
    "response"=>
     {"status"=>{"code"=>200, "message"=>"OK "},
      "headers"=>
       {"Content-Type"=>["text/html;charset=utf-8"],
        "Content-Length"=>["9"],
        "Connection"=>["Keep-Alive"]},
      "body"=>{"encoding"=>"UTF-8", "string"=>"Hello bar"},
      "http_version"=>nil},
    "recorded_at"=>"Tue, 01 Nov 2011 04:58:44 GMT"}],
 "recorded_with"=>"VCR 2.0.0"}

When I run ruby cassette_ruby.rb

Then it should pass with:

Hello foo
Hello bar

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